Battle of Lucius
Dispatching Lucius’ Legio Cybernetica and a great host of battle servitors to the planet’s surface, the Tech-Priests Dominus largely fought their battles from below the planet’s crust. By tracking the motions of their servant clades and controlling their activities via electromagnetic data-tethers, they waged their war without risking direct harm. Such is the wonder of the Cant Mechanicus that their battle plans were enacted to the letter. Wherever the Tyranid swarms overcame their servitor armies, the Tech-Priests waited for the xenos predators to devour the biological components before sending servo-skull swarms to carry the most vital of the remaining machine parts below the crust of the planet. There they were installed into fresh recruits, and the next wave sent back up to the surface. Though it took months to accomplish, the resultant war of attrition ended in victory, for the Lucian armies fought like lions, and their hymns to the Omnissiah’s glory did not cease for a single moment.